1. Field of the Invention
The invention generally relates to solar energy conversion systems and more particularly to a collection system particularly suited for use in collecting solar energy and converting the collected energy to other forms of usable energy such as thermal, electrical and the like.
The sun, of course, comprises a substantially non-destructive source of energy available for continuous exploitation. It has long been recognized that radiant solar energy can and should be utilized to a greater extent in order to reduce dependence upon fossil fuels as sources of usable energy.
Unfortunately, those systems heretofore employed in collecting and utilizing solar energy generally lack efficiency of an order of magnitude necessary for effectively competing with fossil fuels. Efforts to provide new systems, as well as to improve existing systems and techniques are continuously being made at all levels in attempting to acquire and utilize energy derived from solar sources at reduced costs. The likelihood of success of the efforts now being made depends largely upon the cost effectiveness of the systems when employed in collecting and converting solar energy to usable forms of energy.
2. Description of the Prior Art
One direction taken in attempting to enhance cost-effectiveness encompasses a use of a field of heliostats comprising a plurality of reflective surfaces, each having a capability for concentrating a beam of solar energy on a collector equipped with an energy conversion unit adapted to collect and convert radiant solar energy to usable forms of energy such as electrical and thermal forms. Those engaged in the search for systems and techniques capable of collecting and converting solar energy at reduced costs can readily appreciate that the prior art contains numerous descriptions of systems which employ reflector and receiver combinations through which radiant solar energy is concentrated and converted to a more usable form of energy, such as electrical or thermal energy.
The prior art energy collection systems are characterized by centralized energy receivers which capture concentrated beams of radiant energy directed toward the receivers by solar energy reflectors. One such system utilizes energy receivers supported on a tower above an array of energy reflectors, such as a heliostat field. Unfortunately, a significant loss of ground area attends the use of such a system. As can be appreciated the loss is occasioned by the space occupied by the base for the tower, as well as by the space normally occupied by the heliostat field utilized for reflecting incident beams of radiant solar energy toward the receivers.
Where reflectors are mounted near the base of a tower, the attendant loss of area, of course, is minimal. However, such arrangements generally provide for poor intercept angles, particularly where the receivers are mounted atop supporting towers for intercepting beams reflected from surfaces near the base of the tower. Although beams reflected from the edges of a heliostat field are characterized by good angles of incidence, relative to the receivers, dispersion of the beams due to pointing errors tend to dilute solar flux. Consequently, a major portion of the flux field established by reflected beams may be lost because of poor interception. This, of course, can be overcome, generally, by increasing the relative size of the target area of the receiver. However, an increase in the size of the target area tends to increase construction and maintenance costs disproportionately to the increases realized in the level of the system's efficiency. Moreover, precise uniformity in flux distribution normally is not obtainable. Hence, because of a lack of uniformity in flux distribution an increase in temperature differentials occurring across the system is experienced with an attendant reduction in overall efficiency.
Another parameter which must be considered by designers of solar energy collection systems is wind-loading. In those geographical areas in which solar energy collection systems are used with greatest effectiveness, a greater average wind-loading of supporting towers can be expected. Unfortunately, the towers heretofore proposed generally are characterized by a low strength-to-cost ratio. The criticality of this parameter can be more fully appreciated when it is recognized that a failure of a single tower not only removes the energy collection system from an on-line status, but inherently requires extensive repair at an inordinate expense.
Finally, energy collection systems which employ tower-mounted receivers supported above a heliostat field generally lack a capability for expansion, without redundant add-on facilities. Of course, redundant add-on facilities necessitate excessive expenditures of capital.
It should, therefore, be apparent that there currently exists a need for a simple efficient system through which solar energy can be collected and converted to a usable form and utilized more effectively, efficiently, and economically.
It is, therefore, the general purpose of the instant invention to provide an improved energy collection system particularly suited for use in collecting energy from solar sources, characterized by a simple, economic, and efficient combination of improved receivers, supported by an improved array of radially oriented booms above an improved field of heliostats, whereby the efficiency and cost effectiveness of radiant energy collection systems generally are enhanced.